1. Field of the Invention
The present invention relates to an apparatus for rubbing a liquid crystal alignment layer, and particularly to an apparatus for rubbing a liquid crystal alignment layer so that particles released from an alignment layer rubbing process can be removed and that yield rate of liquid crystal display panels can be raised after the alignment layer rubbing process.
2. Description of Related Art
A process for manufacturing Thin Film Transistor-Liquid Crystal Displays (TFT-LCDs) can be divided into three procedures, namely: firstly, a process for manufacturing array substrates and color filters; secondly, a process for display panel assembly including alignment layer rubbing, liquid crystal filling, and sealing; and thirdly, a process for manufacturing liquid crystal modules including assembly of polarizing sheets, backlight sheets and display panels. With respect to the process for display panel assembly, a process for rubbing alignment layers takes a significant and critical role. The alignment layer rubbing process not only takes an important role in controlling the order and orientation of liquid crystal alignment layers, but also maintains the characteristics for a high-quality display including viewing angle, reaction speed, contrast, and color expression.
To align an alignment layer refers to orientation for liquid crystal molecules, with the purpose of making a unified and consistent orientation or an orientation arrangement for the liquid crystal molecules allover or at part of a liquid crystal display (LCD) panel. The purpose for aligning the alignment layer in an LCD is that, when the liquid crystal molecules are driven by an electric field, part of or all of the liquid crystal molecules require a synchronous and consistent action, so that display actions can be prompt and unified. To achieve such a purpose, the procedure of alignment becomes necessary.
Currently, flannelette rubbing rollers are mostly employed in an apparatus for rubbing alignment layers, such that a contacting mechanical rubbing may be applied to the substrates having alignment layers and that a regular pretilt angle may be produced for the alignment layers. Accordingly, the liquid crystal on the alignment layers is formed with a pretilt angle. Such a technique has been adopted for TFT-LCD manufacture until presently due to the merits, such as a shorter operation time. The operation can be performed under normal temperature; and superior characteristics on mass production. Nevertheless, the contacting mechanical rubbing bears shortcomings, for example: the material for making rubbing cloth polyimide has characteristics of high polarization and high absorbency, so that during storage or delivery, the material tends to deteriorate, making an un-uniform alignment. Further, problems incurred during the alignment layer rubbing process, such as dust particles, static electricity, contamination on rubbing cloth breakage, or rubbing scores, will lower yield rate of production.
U.S. Patent Publication No. 2004/0198182 discloses an apparatus for rubbing the alignment layer in an LCD substrate, as shown in FIG. 4. The apparatus comprises a platform 320, a conveyor 312, a base plate 310, a rubbing roller 302, and a conditioning roller 304. When a substrate 300, which has an alignment layer 301, is disposed on the base plate 310, the conveyor 312 will carry and move the base plate 310, together with the substrate 300 disposed on the base plate 310, along direction B, where the alignment layer 301 will be rubbed by the rubbing cloth 306 of a rubbing roller 302. The conditioning roller 304 is located at one side of the rubbing roller 302, such that when the rubbing roller 302 proceeds with a rubbing process, a conditioning cloth 308 of the conditioning roller 304 will contact and smoothen the rubbing cloth 306 of the rubbing roller 302. However, during the rubbing process, contamination from dust particles and rubbing or conditioning cloth breakage, or the problem of rubbing score, exists, resulting in an undesirable yield for the manufacturing process. Besides, since the apparatus for rubbing the alignment layer 301 is equipped with two rollers (i.e. the rubbing roller 302 and the conditioning roller 304), cost raise on manufacture of the apparatus becomes inevitable.
Therefore, during the rubbing process on the alignment layer, it becomes a critical issue as to how to maintain a smooth rubbing cloth on the rubbing roller so as to avoid contamination from dust particles and rubbing or conditioning cloth breakage or the problem of rubbing score, and eventually to lower the cost for manufacturing the apparatus for rubbing the alignment layers.